1. Field of the Invention
In general, the present invention relates to systems that filter out adverse characteristics that may be present in a power transmission from a power supply. More particularly, the present invention relates to the systems that provide voltage surge protection, EMI/RFI protection and/or in-rush current suppression to a power transmission.
2. Prior Art Statement
The prior art is replete with different types of devices and circuits that filter out undesired electrical characteristics from an incoming source of electricity. In the United States of America, most every home and business is supplied with power from a utility company. Typically, the power supplied from the utility company passes through a transformer and is supplied to a building with an alternation current of 120 volts and a nominal frequency of 60 Hz. Although the power at the utility company is generated at these voltages and frequency values, the actual power received at a particular home or business can vary widely depending upon both how the power is transmitted and how the power is used.
Power transmission lines emanating from utility companies are commonly exposed to the elements as they travel from the utility company to a home or business. As such, the power transmission lines are subject to lightning strikes, interference from sun flares, storm damage and the like. All of these occurrences can create abnormalities in the characteristics of the power being transmitted in the transmission line. For example, a lightning strike in a power transmission line can create a large voltage spike in the power being transmitted. If this voltage spike is received by a home or business, the voltage spike can cause damage to many electronic items that experience the voltage spike. Alternatively, power can be disrupted if the spike causes a circuit breaker to trip.
Similarly, power transmission lines can receive electromagnetic interference (EMI) and/or radio frequency interference (RFI) from natural and manmade sources. The resulting EMI/RFI signals cause noise in the characteristics of the power transmission that can disrupt sensitive electronic circuits that receive such power transmissions.
Power transmissions with undesirable characteristics can also be created by the way power is used in a home or business. Many electronic devices draw a higher current when they are first turned on. This is because the circuits in the electronic device are cold and the capacitors in the circuits are not charged. However, soon after the circuit is powered, the current drawn by that circuit can decrease dramatically. As a result, when an electronic device is first turned on, there is an inrush of current, thereby causing a current spike. If multiple electrical devices are all turned on at once, the inrush current spike can be quite large and either cause a circuit breaker to trip or cause damage to the electronic components of those devices that experience the current spike.
In the prior art, there are many different filtering devices that are used to eliminate adverse characteristics from a power supply. However, many of these filters are designed to filter out only one type of adverse characteristic. For example, there are many types of commercially available surge protector items that can eliminate voltage spikes caused by lightning. Such prior art surge protectors are exemplified U.S. Pat. No. 4,870,534 to Harford, entitled Power Line Surge Protector. However, such prior art surge protection devices do not protect from EMI/RFI signal interference or incidents of inrush current.
Similarly, devices exist in the prior art record that are designed to filter EMI/RFI signal interference from power supplies. Such prior art filters are exemplified by U.S. Pat. No. 5,530,396 to Vlatkovic, entitled EMI Input Filter Power Factor Correction Circuits. However, such prior art devices do not filter out voltage surges or inrush current surges.
Lastly, devices exist in the prior art that are designed to eliminate inrush current surges. Such prior art devices are exemplified by U.S. Pat. No. 4,573,113 to Bauman, entitled Surge Protection System For A D-C Power Supply During Power-up, and U.S. Pat. No. 5,930,130 to Katyl, entitled Inrush Protection Circuit. However, such prior art devices do not filter out EMI/RFI signal interference or voltage surges.
A need therefore exists for an improved filtering system that is capable of eliminating voltage surges, EMI/RFI signal interference and inrush current spikes from a power source. This need is met by the present invention as described and claimed below.
The present invention is a system and method for conditioning a power transmission, thereby eliminating adverse characteristics from the power transmission. The system includes a voltage surge protector, an EMI/RFI filter and at least one inrush current suppressor integrally formed into a single system. To condition an incoming power transmission, the power transmission is first passed through the voltage surge protector to eliminate any abnormal voltage spikes. The power transmission is then passed through an improved EMI/RFI filter having a dual output. The outputs of the EMI/RFI filter lead into a first inrush current suppressor. The inrush current suppressor limits the amperage of the power transmission for a predetermined period of time and then permits unrestricted current flow. The inrush current suppressor also can be used as an on/off switch to stop the power transmission. The on/off state of the inrush current suppressor is dependent upon the receipt of an external control signal by the inrush current suppressor.
Electronic equipment receives the power transmission through the circuitry of the inrush current suppressor. Multiple inrush current suppressors can be arranged in a cascading system to power many different collections of electronic equipment. As one inrush current suppressor is activated, it generates a time delayed control signal that can be used to activate a subsequent inrush current suppressor. In this manner, different collections of equipment can be turned on in a controlled sequence that does not surpass the amperage rating of the circuit breaker through which the power transmission is passed.